Lens Array Sheet, Light Source and Liquid Crystal Display Device

ABSTRACT

A lens array sheet includes a lens layer having a lens surface on which a plurality of lenses are formed in an array, a light reflection layer arranged at an opposite side to the lens surface of the lens layer and having an opening within a light focusing region in the lenses to transmit light, for reflecting light at a site other than the opening, and a light diffusion layer arranged between the lens layer and the light reflection layer, for diffusing light, which passes through the opening and is directed toward the lens layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens array sheet, a light source anda liquid crystal display device.

2. Description of the Related Art

Recently, a liquid crystal panel such as liquid crystal display devicehas been gradually enlarged. Although the liquid crystal panel may beenlarged, it is not allowed to degrade the image quality of the paneland it is demanded that high definition image quality of the panel canbe achieved even for a large-scale screen. In order to achieve the highdefinition image quality for the large-scale screen, for example, it isstrongly demanded that brightness of the screen can be maintained orimproved, or viewing angle can be widened. In accordance with thesedemands, some techniques have been proposed to arrange a micro arraylens in the liquid crystal panel and improve the brightness and theviewing angle of the liquid crystal panel. Arranging the micro arraylens makes it possible to enhance front face brightness and/or widen theviewing angle.

On the contrary, there is an issue to be solved, because moire fringesmay appear and visibility may become lower due to the fact that theliquid crystal panel includes an array of regular pixels (i.e., pictureelements). The moire fringes are a fringe pattern which is produced byoverlapping a plurality of regular repetitive patterns and visuallyobserved by a deviation of periods between the plurality of regularrepetitive patterns. The moire fringes in the liquid crystal panel areproduced as each pixel in the liquid crystal panel forms a regularrepetitive pattern and other members and the like has a similar regularrepetitive structure.

Japanese Patent Application Laid-Open No. 2000-206529 discloses moirefringes as mentioned above and a method of reducing such moire fringes.

An optical sheet having a structured pattern of a regular pitch may beused as a launching member for guiding light from a backlight to aliquid crystal panel. In this case, overlapping of pixels forming theregular pitch of the liquid crystal panel and the structured pattern ofthe optical sheet overlaps light and dark lattices and causes moirefringes to be produced. A liquid crystal display device disclosed inJP-A No. 2000-206529 is arranged to reduce the moire fringes byconfiguring an array pitch of pixels and the pitch of the structuredpattern of the optical sheet so as to minimize a pitch distance of themoire fringes. In other words, the liquid crystal display device isarranged to reduce effects of the moire fringes on the image quality byminimizing the pitch distance of the moire fringes and thus decreasingthe pitch distance to a level not more than resolution of human eye.

SUMMARY OF THE INVENTION

Though the liquid crystal display device described in JP-A No.2000-206529 may reduce the effects of the moire fringes on visibilityand the like, actually the moire fringes may appear. Moreover, it isdifficult to adjust the array pitch of the pixels, since there is a needfor modifying a design of the liquid crystal panel itself and amanufacturing line of the liquid crystal panel. Thus, a technique hasbeen developed to suppress moire fringes per se from being produced.

JP-A No. 2000-284268 and JP-A No. 2007-256575 disclose some techniquesto suppress moire fringes per se from being produced. JP-A No.2000-284268 and JP-A No. 2007-256575 propose transparent liquid crystaldisplay devices, respectively, in which each of the transparent liquidcrystal display devices includes a backlight unit using a brightnesscontrol member having a lens array structure containing repetitive lensunit. Each of the liquid crystal display devices includes a liquidcrystal panel and a light source unit for emitting light from a backside of (immediately below) the liquid crystal panel. The light sourceunit also includes a light source, a lens array layer for guiding thelight from the light source to the liquid crystal panel, and a lightshielding section having an opening arranged close to a focal plane ofthe lens array layer (i.e., a back surface opposite to a surface onwhich a lens array is formed). With this arrangement, as described inJP-A No. 2000-284268 and JP-A No. 2007-256575, the moire fringes aresuppressed from being produced by converting the light from the lightsource into parallel light to reduce a structured pattern of an opticalsheet.

It is difficult, however, to sufficiently suppress the moire fringesfrom being produced using the lens array layer as described above. Inother words, since the lens array layer per se also has a regularstructured pattern and the regular structured pattern has effects on theparallel light, it is difficult to convert the light from the lightsource into perfectly parallel light.

Therefore, the present invention has been made in view of theabove-mentioned issues, and it is desirable to provide a new andimproved lens array sheet, light source and liquid crystal displaydevice in which it is possible to suppress degradation of the imagequality and reduce effects of moire fringes on the image quality.

According to an embodiment of the present invention, in order to solvethe above-mentioned issues, there is provided a lens array sheetincluding a lens layer having a lens surface on which a plurality oflenses are formed in an array, a light reflection layer arranged at anopposite side to the lens surface of the lens layer and having anopening within a light focusing region in the lenses to transmit light,for reflecting light at a site other than the opening, and a lightdiffusion layer arranged between the lens layer and the light reflectionlayer, for diffusing light, which passes through the opening and isdirected toward the lens layer.

With this arrangement, light emitted from a side of the light reflectionlayer to the lens array sheet is in part reflected at the lightreflection layer. In addition, a part of the light emitted to the lightfocusing region in the plurality of lenses passes through the opening.The light having passed through the opening is diffused by the lightdiffusion layer before the light reaches the lens layer. Then, thediffused light reaches the lens layer and converted into generallyparallel light by means of the plurality of lenses. It is noted that thelight to be converted into the generally parallel light is diffused. Asa result, after conversion into the generally parallel light by means ofthe lenses, the light turns out to be the generally parallel light,while brightness change of the light between dark and light intensitydue to an array pattern of the plurality of lenses in the lens layer isreduced.

The light diffusion layer may also include a plurality of lightdiffusion portions arranged within the light focusing region in thelenses, for diffusing the light passing through the opening anddirecting toward the lens layer and transparent portions arrangedbetween the light diffusion portions, for transmitting the light.

Each of the light diffusion portion may also have a shape such that awidth of the shape gradually widens as the width approaches to the lenslayer.

The lens array sheet may also include a transparent layer arrangedbetween the light diffusion layer and the light reflection layer, fortransmitting the light.

The lens array sheet may also include a transparent layer arrangedbetween the lens layer and the light diffusion layer, for transmittingthe light.

A haze of the light diffusion layer may be equal to or less than 20%.

The light reflection layer may be a scatter and reflection layer forscattering light in order to reflect the light.

The light reflection layer may not be formed at least around the lensarray sheet.

A lenticular lens may also be formed on the lens surface of the lenslayer in which the lenticular lens includes a plurality of convexcylindrical lenses arranged in parallel to each other and at apredetermined distance.

According to another embodiment of the present invention, in order tosolve the above-mentioned issues, there is provided an optical sheetincluding a lens array sheet having a lens surface on which a pluralityof lenses are formed in an array, and a light diffusion plate arrangedat an opposite side to the lens surface of the lens array sheet, fordiffusing light directing toward to the lens array sheet, wherein thelens array sheet includes a lens layer having the lens surface, and alight reflection layer arranged at an opposite side to the lens surfaceof the lens layer and having an opening within a light focusing regionin the lenses to transmit light from the light diffusion plate, forreflecting light at a site other than the opening, and a light diffusionlayer arranged between the lens layer and the light reflection layer,for diffusing the light passing through the opening and directing towardthe lens layer.

The optical sheet may also include a polarization splitting filmarranged at a lens surface side of the lens array sheet, forpolarization splitting light.

The optical sheet may also include a light diffusion sheet arranged atleast one of between the polarization splitting film and the lens arraysheet and between the lens array sheet and the light diffusion plate,for diffusing light.

Furthermore, according to another embodiment of the present invention,in order to solve the above-mentioned issues, there is provided a lightsource including a lens array sheet having a lens surface on which aplurality of lenses are formed in an array, and a backlight arranged atan opposite side to the lens surface of the lens array sheet, foremitting light on the lens array sheet, wherein the lens array sheetincludes a lens layer having the lens surface, a light reflection layerarranged at an opposite side to the lens surface of the lens layer andhaving an opening within a light focusing region in the lenses totransmit the light emitted from the backlight, for reflecting light at asite other than the opening, and a light diffusion layer arrangedbetween the lens layer and the light reflection layer, for diffusing thelight passing through the opening and directing toward the lens layer.

Furthermore, according to another embodiment of the present invention,in order to solve the above-mentioned issues, there is provided a liquidcrystal display device including a lens array sheet arranged between aliquid crystal panel and a backlight emitting light on the liquidcrystal panel and having, at a side of the liquid crystal panel, a lenssurface on which a plurality of lenses are formed in an array, whereinthe lens array sheet includes a lens layer having the lens surface, alight reflection layer arranged at an opposite side to the lens surfaceof the lens layer and having an opening within a light focusing regionin the lenses to transmit the light emitted from the backlight, forreflecting light at a site other than the opening, and a light diffusionlayer arranged between the lens layer and the light reflection layer,for diffusing the light passing through the opening and directing towardthe lens layer.

According to the embodiments of the present invention described above,effects of moire fringes on the image quality can be reduced whilesuppressing the image quality being degraded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram for explaining a configuration of alens array sheet according to a first embodiment of the presentinvention;

FIG. 2 is an explanatory diagram for explaining a configuration of thelens array sheet according to the embodiment;

FIG. 3 is an explanatory diagram for explaining a configuration of alens array sheet according to a second embodiment of the presentinvention;

FIG. 4 is an explanatory diagram for explaining a configuration of alens array sheet according to a third embodiment of the presentinvention;

FIG. 5 is an explanatory diagram for explaining a configuration of alens array sheet according to a fourth embodiment of the presentinvention;

FIG. 6 is an explanatory diagram for explaining a configuration of alens array sheet according to a fifth embodiment of the presentinvention;

FIG. 7 is an explanatory diagram for explaining a configuration of alens array sheet according to a sixth embodiment of the presentinvention;

FIG. 8 is an explanatory diagram for explaining a configuration of thelens array sheet according to the embodiment;

FIG. 9 is an explanatory diagram for explaining a configuration of alens array sheet according to a seventh embodiment of the presentinvention;

FIG. 10 is an explanatory diagram for explaining a configuration of alens array sheet according to an eighth embodiment of the presentinvention;

FIG. 11 is an explanatory diagram for explaining a configuration of alens array sheet according to a ninth embodiment of the presentinvention;

FIG. 12 is an explanatory diagram for explaining a configuration of thelens array sheet according to the embodiment;

FIG. 13 is an explanatory diagram for explaining a configuration of alens array sheet according to a tenth embodiment of the presentinvention;

FIG. 14 is an explanatory diagram for explaining a configuration of aliquid crystal display device according to an eleventh embodiment of thepresent invention; and

FIG. 15 is an explanatory diagram for explaining a configuration of aliquid crystal display device according to a twelfth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the appended drawings, structural elementsthat have substantially the same function and structure are denoted withthe same reference numerals, and repeated explanation of thesestructural elements is omitted.

First, a lens array sheet according to each of embodiments of thepresent invention will now be described. Then, an optical sheet, a lightsource, and a liquid crystal display device using these lens arraysheets will be described.

The lens array sheet according to each of the embodiments of the presentinvention includes a layer or a site for diffusing light, for example,to reduce effects of moire fringes on the image quality whilesuppressing the image quality from being degraded. In addition, theembodiments of the present invention may be classified into two groupsdepending on a shape or an arrangement position of a light diffusionlayer or site, other structures and the like. Consequently, embodiments(i.e., a first embodiment to a sixth embodiment) concerning one group ofthe present invention will be first described and other embodiments(i.e., a seventh embodiment to a tenth embodiment) of the presentinvention will be then described. It is noted that since thoseembodiments have many common elements, repeated explanation of the samecontents in subsequent embodiments will be conveniently omitted and thedifferences between the embodiments will be described.

Lens Array Sheet 101 According to First Embodiment

Referring to FIG. 1 and FIG. 2, a configuration of a lens array sheetaccording to the first embodiment of the present invention will now bedescribed. FIG. 1 and FIG. 2 illustrate the configuration of the lensarray sheet according to this embodiment. In FIG. 1 and FIG. 2,schematic sectional shape and configuration of the lens array sheetaccording to this embodiment are shown, respectively. It is noted thatthe sectional shape of a right-side end portion of the lens array sheet101 is shown and a part of the lens array sheet 101 located at a leftside of a line A-A is omitted in FIG. 1.

<Configuration of Lens Array Sheet 101>

As shown in FIG. 1, the lens array sheet 101 according to thisembodiment includes a three-layered structure formed in one piece. Thatis to say, the lens array sheet 101 includes a lens layer 10, a lightdiffusion layer 20A, and a light reflection layer 30.

The lens layer 10 has a lens surface 11 on which a plurality ofindividual lenses (hereinafter, also referred to as “lenses”) U areformed in an array. A surface opposite to the lens surface 11 of thelens array sheet 101 has a generally flat shape. Hereinafter, thissurface is also referred to as a “flat surface”.

In terms of the lens layer 10, for example, one lens array sheet isconfigured such that the lenses U are formed in a one-dimension arraywithin the lens surface 11 and another lens array sheet is configuredsuch that the lenses U are formed in a two-dimension array within thelens surface 11. On one hand, the lens array sheet in the form of theone-dimension array includes, for example, a lenticular lens array sheeton which convex cylindrical lenses are arranged in one direction in anarray within the lens surface 11 and the like. On the other, the lensarray sheet in the form of the two-dimension array includes, forexample, a lens array sheet on which the lenses U are arranged in atwo-dimension array within the lens surface 11 and the like, whereineach of the lenses U has a circular, rectangular, hexagonal, orpolygonal shape or the like and is formed of a dome-shaped curvedsurface.

The plurality of lenses U, which are formed on the lens surface 11 ofthe lens layer 10, are regularly arranged with a predetermined distance(pitch) either in one direction in case of the one-dimensional array orin two directions in case of the two-dimensional array.

Each of the lenses U has a focal point F on the side of the flatsurface. By arranging a light source at the focal point F and emittinglight to the lens U, this light is converted into parallel lightdirecting along a normal direction of the lens surface 11 by means ofthe lens U. In FIG. 1, an optical path P denotes the light to beconverted into the parallel light. As to the focal point F and theoptical P, it can be said that each of the lenses U focuses the parallellight on the focal point F in case where the parallel light is emittedfrom the upper part of this drawing. A region through which the lightbeing focused on the focal point F passes is herein referred to as a“light focusing region G”. A region other than the light focusing regionG is also herein referred to as a “non-light focusing region N”.Furthermore, surfaces in parallel with the lens array sheet 101 in thelight focusing region and the non-light focusing region are referred toas a “light focusing surface region” and a “no-light focusing surfaceregion”, respectively.

The lens layer 10 may be made of a material such as glass and plasticmaterial, but the present invention is not limited to such an example.Examples of the plastic material include, for example, homopolymer orcopolymer of acrylic ester or methacrylic ester such as methylpolymethacrylate and methyl polyacrylate, and a resin material ofpolyester, polycarbonate, polystyrene and the like such as polyethyleneterephthalate and polybutylene terephthalate.

The light diffusion layer 20A is laminated on the flat surface of thelens layer 10 and formed integrally with the lens layer 10. In short,the light diffusion layer 20A is arranged between the lens layer 10 andthe light reflection layer 30. Thus, the light diffusion layer 20Adiffuses light, which passes through the light diffusion layer 20A. Apart of the light diffusion layer 20A is herein referred to as a “lightdiffusion portion 21”. To achieve such light diffusion layer 20Adiffusing the light, for example, a layer can be used that disperses adiffusion agent in a light transparent resin and utilizes a lightscattering effect due to the difference in refractive index between thediffusion agent and the light transparent resin.

On one hand, for example, it is possible to use beads or filler, orhollow beads mainly containing acryl resin, polystyrene, polyethylene,urea resin, urethane resin, organic silicone resin, calcium carbonate,titanium oxide, silica and the like as the diffusion agent. Desirably,an average particle size of the diffusion agent is, for example, in therange of about 1 to 50 μm so that the diffusion agent is easy to use. Inaddition, a combination of two or more kinds of diffusion agents may beused having different types and particle sizes.

On the other, for example, it is possible to use polyester resin,acrylic resin, polystyrene resin, polyvinyl chloride resin,polyvinylidene chloride resin, polyethylene resin, polypropylene resin,polyurethane resin, polyamide resin, polyvinyl acetate resin, polyvinylalcohol resin, epoxy resin, cellulose resin, silicone resin, polyimideresin, polysulfone resin, polyarylate resin and the like as the lighttransparent resin.

In addition, preferably, a material having refractive index lower thanthat of the lens layer 10 may be used as the light transparent resinamong the above-mentioned materials. Using such material enables a lightbeam to be directed more closely to a normal direction of the sheet dueto the difference in the refractive index, as the light is incident fromthe light diffusion layer 20A to the lens layer 10. Therefore, the lensU in the lens layer 10 can work just as designed to develop lens effects(including an effect of changing an optical path and the like).

In addition, preferably, the light diffusion layer 20A has a haze of notmore than 20%. In case of the haze being above 20%, since a lightdiffusion effect of the haze on the light diffusion layer 20A becomesstronger and an amount of light passing through the lens array sheet 101decreases, front face brightness may probably goes down. Furthermore, incase of the haze being above 20%, it may be difficult to achieve a lightfocusing effect via the lens layer 10. In addition, a haze value of thelight diffusion layer 20A may be adjusted by selecting materials of thediffusion agent and the light transparent resin, respectively, andadjusting the average particle size of the diffusion agent.

The light reflection layer 30 is laminated on a surface opposite to asurface that contacts with the lens layer 10 of the light diffusionlayer 20A, and formed integrally with the light diffusion layer 20A. Inshort, the light reflection layer 30 is arranged at a side of thesurface opposite to the lens surface 11 of the lens layer 10. Then, thelight reflection layer 30 reflects light at the light reflection portion31. In this case, the light reflection portion 31 may be formed as ascattering reflection layer, for example, that reflects light byscattering the light. Although, such light reflection portion 31 thatreflects the light may be, for example, made of a metal material such asaluminum, silver, zing and the like, various materials may be used asthe material of the light reflection portion 31, the present inventionis not limited to such an example.

The light reflection layer 30 has an opening 32 through which lightpasses. In short, light emitted from the lower part of this drawingpasses through the opening 32 and reaches the light diffusion layer 20A.The light diffusion layer 20A then diffuses light that passes throughthe opening 32 and directs toward the lens layer 10.

The opening 32 is formed within the light focusing region of the lens Uat a location corresponding to a top site of the lens U. In this case,desirably, the opening 32 is not formed in the non-light focusingregion. That is to say, for example, in the case where light is emittedby arranging a light source at a focal point F, the opening 32 isconfigured such that it transmits at least a part of one light passingthrough the light focusing region G of each of the lenses U and does nottransmit the other light including light that passes through thenon-light focusing region N. As shown in FIG. 1, the opening 32transmits all of lights that run through the light focusing region, buta size of the opening 32 according to this embodiment is not limited tosuch an example. For example, the size of the opening 32 may be suchthat it does not transmit the light that passes through the non-lightfocusing region N or such that it transmits the part of the light thatpasses through the light focusing region G. If the size of the opening32 is sufficiently large so as to reach the non-focusing region N, thena light component that can be rarely sufficiently restricted isincreased. In this case, a light component that is not converted intoparallel light by the lens U (i.e., light that is not emitted along anormal direction of the sheet) increase. To the contrary, if the size ofthe opening 32 is made small even within the light focusing region G, alight component, which is restricted to the focal point F in a moreuniform way, is incident on the lens U and light emitted from the lenslayer 10 more and more approximates parallel light. In this case,however, a variation of an amount of an emitted light may probablyincrease. Therefore, shapes and sizes of the lens U and the opening 32,respectively, are desirably determined based on performance requestedfor the lens array sheet 101 (i.e., conversion efficiency, an amount oflight to be transmitted (front face brightness) and the like), a size ofthe lens array sheet 101 or a positional relation between the lens arraysheet 101 and the light source and the like. Thus, sectional shapes ofthe lens U and the opening 32, respectively, may be any shape such assquare, circle, ellipse, rectangular, diamond, polygon or the like.Furthermore, the sectional shapes of the lens U and the opening 32,respectively, may be, for example, formed in a band shape that iscontinuously extended along one direction (such lens is referred to as alenticular lens). In other words, the shape of the opening 32 may beformed in a shape corresponding to a light focusing surface of the lensU.

Since the light reflection layer 30 has this opening 32, the lightreflection layer 30 can mainly transmit light, which is to be convertedinto generally parallel light by the lens U, that is to say, whichapproximately passes through the focal point F and reflect many otherlights that would not be converted into the generally parallel light.Therefore, since the lens array sheet 101 has the light reflection layer30, the lens array sheet 101 can enhance an effect of the lens layer 10and convert the light into the generally parallel light.

In addition, the light reflection layer 30 (light reflection portion 31)that reflects light is, desirably, not formed at an end, that is to say,at a periphery E of the lens array sheet 101. In other words, it can besaid that the light reflection layer 30 has another opening at theperiphery E of the lens array sheet 101. An amount of light passingthrough the periphery E of the lens array sheet 101 is expected to beless than that of light passing through a center of the lens array sheet101. Therefore, the light reflection layer 30 does not reflect the lightpassing through the periphery E so that it can suppress a reduction ofthe amount of the light in the periphery E. In addition, the lightfocusing effect that converts the light into the generally parallellight by the lens layer 10 is weakened by suppressing the lightreflection layer 30 from being formed on the periphery E. As a result, aproduction of moire fringes would also be restricted in the periphery E.In addition to the light reflection layer 30, the lens U of the lenslayer 10 may be omitted from the periphery E of the lens sheet array101.

<Example of Dimensions for Lens Array Sheet 101>

Hereinbefore, a configuration of the lens array sheet 101 according tothis embodiment have been described. Referring to FIG. 2, exemplarydimensions of each of configurations in this lens array sheet 101 willnow be described.

In FIG. 2, a lens layer 10, a light diffusion layer 20A and a lightreflection layer 30 corresponding to one lens U are shown. A width of asingle lens is denoted by L, a distance from a flat surface of the lenslayer 10 to a focal point F is denoted by S, a thickness of the lightdiffusion layer 20A is d, and a width of a light reflection portion 31corresponding to the single lens U is denoted by Wr. The width Wr of thelight reflection portion 31 then can be set to satisfy the followingcondition (Formula 1).

$\begin{matrix}{{Wr} \geq \left\{ \begin{matrix}\frac{L \times d}{2 \times S} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \geq d} \\{L\left( {1 - \frac{d}{2 \times S}} \right)} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \leq d}\end{matrix} \right.} & \left( {{Formula}\mspace{14mu} 1} \right)\end{matrix}$

(Example of Method for Forming Lens Array Sheet 101)

Hereinafter, an example of a method for forming a lens array sheet 101according to this embodiment will be described. The method for formingthe lens array sheet as described herein is merely one example, but isriot intended to limit the present invention. Naturally, the lens arraysheet 101 may be formed using various other methods. In addition, anexample in which a lenticular lens array is used as the lens layer 10 isdescribed, different lenses U having other shapes can also be formed.

First, the lens layer 10 is formed.

The method for forming the lens layer 10 may be any methods including,for example, a method using a mold having a shape corresponding to thelens U, a method for transferring a shape of an nickel stamper having ashape corresponding to the lens U by a heating press process, a methodfor applying an ultraviolet curing resin or an electron curing resin ona transparent substrate etc., embossing the resin by an embossing rollof a shape corresponding to the lens U, and thereafter curing the resinusing ultraviolet ray or electron ray, and a method for forming a lensby forming a photoresist pattern with a pitch of the lens U byphotolithography and heating and melting the photoresist, and the like.

Next, the light diffusion layer 20A is laminated on a flat surfaceopposite to the lens surface 11 of the lens layer 10. In short, thelight diffusion layer 20A is formed integrally with the lens layer 10 byeither applying a material of the light diffusion layer 20A on the lenssurface 11 and curing the material or laminating cured layers.

Thereafter, the light reflection layer 30 having the light reflectionportion 31 and the opening 32 is also laminated on the light diffusionlayer 20A. A method for forming the light reflection layer 30 includes,for example, laminating an ultraviolet curing resin film on the lightdiffusion layer 20A to form an adhesive ultraviolet curing resin layer.Then, a parallel ultraviolet light is emitted to the lens surface 11. Asa result, the ultraviolet curing resin layer in a light focusing regionG to which the parallel light is emitted is cured. A transfer sheet, onwhich a metal material forming the light reflection layer has beenapplied, is then pressurized such that the metal material is opposite tothe ultraviolet curing resin layer. After that, by peeling the transfersheet, the metal material (light reflection portion 31) is attached to anon-light focusing region N using an adhesive of the ultraviolet curingresin layer in a non-curing part. The non-curing part of the ultravioletcuring resin layer is then exposed to a ultraviolet light so that thenon-curing part can be cured. During this time, the ultraviolet lightmay be radiated, for example, from an opposite side of the lens surface11. Consequently, the light reflection layer 30 having the opening 32 inthe light focusing region G is formed integrally at a back side of thelight diffusion layer 20A (a surface opposite to the lens layer 10).

The method for forming the lens array sheet 101 is described by way ofexample only, as described above, and is not indented to limit thepresent invention. In addition, forming the light reflection layer 30 isherein described in terms of using the ultraviolet curing resin, but thelight reflection layer 30 can be formed by various ways such as aphotolithography method, a metal evaporation method, a metal printingmethod, a transfer method, a sputtering method, an ion plating method, amethod for laminating predetermined shaped metals, and the like.

(Example of Advantages of Lens Array Sheet 101)

The configuration of the lens array sheet 101 according to the firstembodiment of the present invention have been described as above. Withthis lens array sheet 101, for example, when the light source isarranged at the side of the light reflection layer 30 and the light isemitted from the light source, light incident on the lens layer 10 isrestricted to the focal point F. Thus, the lens array sheet 101 enablesthe generally parallel light to be emitted from a direction of the lenssurface 11 of the lens layer 10. In this case, the emitted generallyparallel light includes light diffused by the light diffusion layer 20A.Therefore, the lens array sheet 101 can reduce light having a similarpattern as a regular pattern of the lens U or a pattern of the lightreflection layer 30 and included in the generally parallel light (i.e.,the lens array sheet 101 can reduce a pattern of brightness uniformity,a directional pattern or the like). As a result, even if; for example, aliquid crystal panel is arranged in front of the lens array sheet 101,the lens array sheet 101 can reduce a regular light pattern, whichproduces moire fringes with a regular structured pattern of the liquidcrystal panel, and can suppress the moire fringes from being produced.

Advantages of the lens array sheet, such as suppression of the moirefringes and the like, will be described in detail with reference to anexample in which the lens array sheet 101 is used for a liquid crystaldisplay device.

A usual liquid crystal display device has a liquid crystal panel and alight source emitting light to the liquid crystal panel. In addition, itis desirable that the light is restricted to a direction towards a frontsurface of the liquid crystal display device in order to improvevisibility of the liquid crystal display device. As mentioned above, thelens array sheet 101 according to this embodiment can irradiate thelight, which is restricted to the focal point F by the light reflectionlayer 30, on the lens layer 10 so that the generally parallel light canbe emitted from the lens layer 10. Thus, the lens array sheet 101 canimprove the visibility of the liquid crystal display device.

In this case, the liquid crystal display device has regularly arrangedpixels. Thus, moire fringes can be produced when an arrangement pitch ofthe pixels and the structured pattern of the lens array sheet overlap.In this case, if a light focusing effect of the lens of the lens arraysheet were uniformly achieved, then production of the moire fringeswould be rather facilitated. However, the lens array sheet 101 accordingto this embodiment has the light diffusion layer 20A between the lightreflection layer 30 and the lens layer 10. This light diffusion layer20A diffuses light incident on the lens layer 10. In this manner, sincethe diffused light is incident on the lens layer 10, the light focusingeffect of the lens decreases and the moire fringes are suppressed frombeing produced.

However, if the light focusing effect of the lens (a bright improvingeffect, a light distribution effect or the like) is too much suppressed,then a component of the generally parallel light, which is emitted fromthe lens array sheet, may decrease, an amount of the light, which may beemitted to a front surface of the liquid crystal display device, andvisibility of the liquid crystal may be degraded. To the contrary, inthe lens array sheet 101 according to this embodiment, the lightdiffusion layer 20A diffuses light directing toward the lens layer 10after the light has been restricted to the focal point F by the lightreflection layer 30 and immediately before the light is incident on thelens layer 10. Therefore, the light incident on the lens layer 10 wouldnot be significantly diffused. Consequently, the lens array sheet 101can maintain the light focusing effect of the lens to the extent thatthe visibility is not degraded while suppressing the moire fringes frombeing produced.

In addition, it is also conceivable that a light diffusion plate isarranged outside the lens array sheet 101 in order to diffuse light ifit is solely intended to cancel parallel light and suppress moirefringes from being produced. In this case, with regard to an arrangementposition of the light diffusion plate being arranged outside the lensarray sheet, it is conceivable that the light diffusion plate may bearranged on a side of the lens surface 11 of the lens layer 10 or on aside of the light reflection layer 30. However, if sufficiently manydiffusion plates, which diffuse light, to suppress the moire fringesfrom being produced is arranged out side the lens array sheet 101, anumber of interfaces between layers increase. As a result, due toreflection on the interfaces between the layers, an amount of light,which follows an unexpected optical path, significantly increase so asto suppress effects such as a light focusing effect of the lens etc., abrightness improving effect, a light distribution effect or the like,and light use efficiency would be reduced. In addition, if these effectsare reduced, it becomes difficult to determine a correlation betweendesign factors and the effects, and thereby complicate the design of thelens array sheet itself. Consequently, it would be difficult to providean optimal structure. To the contrary, in case of the lens array sheet101 according to this embodiment, the optical path will not be extremelycomplicated by providing the light diffusion layer 20A between the lenslayer 10 and the light reflection layer 30. Therefore, it is possible toappropriately suppress the moire fringes from being produced withoutencountering the above-mentioned issues.

Differently from this embodiment, in case where the light diffusionplate for diffusing the light is arranged outside on the side of thelens array sheet 101, it leads to an increase of manufacturing cost as anumber of members increase by one. In addition, in case where, forexample, the light diffusion plate is arranged out side of the lenssurface 11 of the lens layer 10, a generally parallel light componentwill decrease. Therefore, the visibility of the liquid crystal displaydevice probably degrade. However, the lens array sheet 101 according tothis embodiment has the light diffusion layer 20A between the lens layer10 and the light reflection layer 30, thereby avoiding theabove-mentioned issues.

In addition, in case where the light diffusion plate is arranged outsideon the of the light reflection layer 30, the light widely scattered bythe light diffusion plate passes through an opening 32, which isdifferent from a desired opening 32, or be incident on a lens U, whichis different from a lens U corresponding to the opening 32 through whichthe light passes. As a result, the effect that the light is restrictedto the focal point F by the light reflection layer 30 will be weakenedand some effects such as a light focusing effect of the lens layer 10will be also weakened. From this point of view, a position, at which thelight is diffused, is preferably located near (in particular,immediately in front of) the lens layer 10 as illustrated in thisembodiment. According to the light diffusion layer 20A of thisembodiment, it is possible to diffuse light, while suppressing the lightfrom being incident on a lens U, which is different from a lens Ucorresponding to an opening 32 through which the light passes.

An example of the advantages of the lens array sheet 101 according tothis embodiment as herein described is also true for other embodimentsas described hereinafter. Therefore, for an explanation of the otherembodiments described below, in addition to the advantages of the lensarray sheet 101 according to this embodiment, further advantages of itwill now be explained.

Hereinbefore, the lens array sheet 101 according to the first embodimentof the present invention has been described. In addition, in the contextof this lens array sheet 101, it has been described that a haze value ofthe light diffusion layer 20A may be adjusted by selecting a material ofthe light diffusion layer 20A and the like. However, an availablematerial of the light diffusion layer 20A may be limited depending on,for example, cost of the material, unavailability of the material,convenience of the design, and the like. When a thick of the lightdiffusion layer 20A becomes very thick, diffusion property of the lightdiffusion layer 20A becomes too high to control the light. That is tosay, light rather than light directing toward a desired direction wouldbe incident on the lens U. In these cases, other embodiments, in whichthe haze value and the diffusion property are, in particular, controlledusefully and appropriately and other advantages are achieved, will nowbe described with reference to FIG. 3.

Lens Array Sheet 102 According to Second Embodiment

FIG. 3 is an explanatory diagram for explaining a configuration of alens array sheet 102 according to a second embodiment of the presentinvention.

(Configuration of Lens Array Sheet 102)

As shown in FIG. 3, the lens array sheet 102 according to thisembodiment includes a transparent layer 40 in addition to configurationsincluded in the lens array sheet 101 according to the first embodiment.

The transparent layer 40 is arranged between a light diffusion layer 20Aand a light reflection layer 30 and formed integrally with the lightdiffusion layer 20A and the light reflection layer 30. In addition, thetransparent layer 40 transmits light between the light diffusion layer20A and the light reflection layer 30. A part of the transparent layer40 is herein also referred to as a “transparent portion 41”. Though thetransparent portion 41 is shown such that it is arranged between thelight diffusion layer 20A and the light reflection 30 with reference tothis embodiment, the transparent portion 41 may be arranged, forexample, between a lens layer 10 and the light diffusion layer 20A.

The transparent layer 40 may be made of a material such as glass andplastic material as is the case with the lens layer 10, but the presentinvention is not limited to such an example.

(Example of Method for Forming Lens Array Sheet 102)

Such transparent layer 40 may be formed, for example, by laminating thetransparent layer 40 on the light diffusion layer 20A before forming thelight reflection layer 30 in the lens array sheet 101 according to thefirst embodiment. Of course, the method for forming the lens array sheetis not intended to limit the present invention.

(Example of Advantages of Lens Array Sheet 102)

Hereinbefore, a configuration of the lens array sheet 102 and the likeaccording to the second embodiment of the present invention have beendescribed. This lens array sheet 102 has an advantage in that it enablesa haze value of the light diffusion layer 20A to be adjusted withoutchanging a total thickness of the lens array sheet 102 by adjusting athickness of the light diffusion layer 20A in addition to the advantagesachieved by the lens array sheet 101 according to the first embodiment.The lens array sheet 102 also makes it possible to make use of effects,such as a reflection effect, a diffusion effect and the like, whichutilize a further added interface between the light diffusion layer 20Aand the transparent layer 40.

Referring to FIG. 4, a third embodiment making use of such interfacewill now be described.

Lens Array Sheet 103 According to Third Embodiment

FIG. 4 is an explanatory diagram for explaining a configuration of alens array sheet according to a third embodiment of the presentinvention.

(Configuration of Lens Array Sheet 103)

A lens array sheet 103 according to this embodiment includes a lightdiffusion layer 20B in place of the light diffusion layer 20A includedin the lens array sheet 101 according to the first embodiment. The lightdiffusion layer 20B has a light diffusion portion 21 similar to a partof the light diffusion layer 20A according to the first embodiment and atransparent portion 41 similar to a part of the transparent layer 40according to the second embodiment.

In one hand, the light diffusion portion 21 is arranged in a lightfocusing region G of a lens U and diffuses light passing through anopening 32 of a light reflection layer 30 and directing toward a lenslayer 10. On the other, the transparent portion 41 is arranged betweenlight diffusion portions 21 and transmits the light.

(Example of Method for Forming Lens Array Sheet 103)

Such light diffusion layer 20B may be formed, for example, by formingthe light diffusion layer 21 and forming the transparent portion 41between the light diffusion portions 21 before forming the lightreflection layer 30 in the lens array sheet 101 according to the firstembodiment. In addition, the light diffusion portion 21 may be eitherformed by removing a part of the light diffusion layer 20A using aphotolithography or sputtering method, or formed by using other printingmethod, transfer method or the like. Alternatively, it is possible tofirstly form the light diffusion layer 20B and then form the lens layer10 and the light reflection layer 30. Of course, the method for formingthe lens array sheet is not intended to limit the present invention.

(Example of Advantages of Lens Array Sheet 103)

Hereinbefore, a configuration of the lens array sheet 103 and the likeaccording to the third embodiment of the present invention has beendescribed. This lens array sheet 103 has an advantage in that it enablesa haze value of the light diffusion layer 20B to be adjusted withoutchanging a total thickness of the lens array sheet 103 by adjusting awidth of the light diffusion portion 21 in addition to the advantageachieved by the lens array sheet 101 according to the first embodiment.In addition, the lens array sheet 103 forms two interfaces between lightfocusing regions of one lens U and the other lens U, as the lens arraysheet 103 has the transparent portion 41 between one and the otherlenses U. These interfaces enable a part of light which is reflectedfrom one of the light diffusion portions 21 and directs to a lens Uother than a lens U corresponding to the one of the light diffusionportions 21, to be reflected toward the lens U corresponding to the oneof them. Therefore, the lens array sheet 103 enables a light useefficiency to be improved and also enables a light focusing effect ofthe lens layer 10 to be improved.

In addition, it is possible to combine the lens array sheet 103according to this embodiment with a configuration of the lens arraysheet 102 according to the second embodiment of the second embodiment.For this purpose, a fourth embodiment and a fifth embodiment of thepresent invention will be now described, which combine those lens arraysheet as described above, respectively.

Lens Array Sheets 104 and 105 According to Fourth and Fifth Embodiments

FIG. 5 is an explanatory diagram for explaining a configuration of alens array sheet according to a fourth embodiment of the presentinvention. FIG. 6 is an explanatory diagram for explaining aconfiguration of a lens array sheet according to a fifth embodiment ofthe present invention.

(Configuration of Lens Array Sheets 104 and 105)

On one hand, a lens array sheet 104 according to the fourth embodimenthas a transparent layer 40 between a lens layer 10 and a light diffusionlayer 20B, as shown in FIG. 5. On the other, as shown in FIG. 6, a lensarray sheet 105 has a transparent layer 40 between a light diffusionlayer 20B and a light reflection layer 30.

(Example of Method for Forming Lens Array Sheets 104 and 105)

Such lens array sheets 104 and 105 can be formed by combining a methodfor forming a lens array sheet 102 according to the second embodimentand a method for forming a lens array sheet 103 according to the thirdembodiment. Of course, the method for forming the lens array sheets 104and 105 is not intended to limit the present invention.

(Example of Advantages of Lens Array Sheets 104 and 105)

Hereinbefore, a configuration of the lens array sheet 104 and 105 andthe like according to the fourth and fifth embodiments of the presentinvention, respectively, have been described. These lens array sheets104 and 105 can have advantages resulting from a combination of theadvantages achieved by the lens array sheet 102 according to the secondembodiment and the lens array sheet 103 according to the thirdembodiment, respectively. In particular, in case of the lens array sheet105 according to the fifth embodiment, the light diffusion portion 21diffuses light immediately before the light is incident on the lenslayer 10. Therefore, it becomes less likely that light passing throughan opening 32 may penetrate into a lens U other than a lens Ucorresponding the opening 32, and the light diffusion portion 21 alsoenables a light use efficiency to be improved.

In the above mentioned third, fourth and fifth embodiments, it is shownthat a light diffusion portion 21 is not a single layer, but has atransparent portion 41 inserted between layers of the light diffusionportion 21, and a shape of the light diffusion portion 21 (i.e., a shapeof the transparent portion 41) is not particularly limited. However, bychanging the shape of the light diffusion portion 21, a furtheradvantage can be achieved. Then, referring to FIG. 7 and 8, a sixthembodiment will now be explained in which the sixth embodiment is basedon the third embodiment and is modified such that a shape of the lightdiffusion portion 21 is changed. Of course, the fourth embodiment andthe fifth embodiment other than the third embodiment may be similarlymodified.

Lens Array Sheet 106 According to Sixth Embodiment

FIG. 7 is an explanatory diagram for explaining a configuration of alens array sheet according to a sixth embodiment of the presentinvention.

(Configuration of Lens Array Sheet 106)

A lens array sheet 106 according to this embodiment has a lightdiffusion layer 20C in place of a light diffusion layer 20B included ina lens array sheet 103 according to the third embodiment as shown inFIG. 7. In addition, the light diffusion layer 20C has a light diffusionportion 22 and a transparent portion 42.

The light diffusion portion 22 may be formed as in the case of the lightdiffusion portion 21, as described above, except for its shape andcorrespondingly the transparent portion 42 may be formed as in the caseof the transparent portion 41, as described above, except for its shape.

The light diffusion portion 22 is arranged in a light focusing region Gof a lens U and has a shape (a width in a direction of a plane in a lensarray sheet 106) gradually widening toward a lens layer 10. In otherwords, the light diffusion portion 22 has a shape following the lightfocusing region G in the light focusing region of individual lenses U.In short, for example, the light diffusion portion 22 may be formed in atruncated cone shape when a section of the lens U is circular and formedin a polygonal frustum shape when the section of the lens U ispolygonal. In addition, the light diffusion portion 22 diffuses lightpassing through an opening 32 of a light reflection layer 30 anddirecting toward the lens layer 10. Furthermore, the transparent portion42 is arranged between light diffusion portions 21 and transmits light.

(Example of Dimensions of Lens Array Sheet 106)

Hereinbefore, a configuration of the lens array sheet 106 according tothis embodiment have been described.

Referring to FIG. 8, an example of dimensions of individualconfigurations in the lens array sheet and the like will now bedescribed.

FIG. 8 illustrates a lens layer 10, a light diffusion layer 20C and alight reflection layer 30 corresponding to a single lens U. A width of asingle lens is denoted by L, a distance from a flat surface of the lenslayer 10 to a focal point F is denoted by S, and a width of a lightreflection portion 31 corresponding to the single lens U is denoted byWr. In addition, a depth from the lens layer 10 in the light diffusionlayer 20C is denoted di, and a width of the light diffusion portion 22at the depth di is denoted by Wi. Then, the width Wi of the lightdiffusion portion 22 can be set to satisfy the following condition(Formula 2).

$\begin{matrix}{{Wi} \leq \left\{ \begin{matrix}{L\left( {1 - \frac{di}{S}} \right)} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \geq {di}} \\{L - {2{Wr}}} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \leq {di}}\end{matrix} \right.} & \left( {{Formula}\mspace{14mu} 2} \right)\end{matrix}$

(Example of Method for Forming Lens Array Sheet 106)

Such light diffusion layer 20C may be formed, for example, as follows.First, an ultraviolet curing resin having light diffusion property isapplied on a flat surface of a lens layer 10 and then an ultravioletlight is emitted from a lens surface 11 of the lens layer 10 in whichthe ultraviolet light has a diameter from a center of a lens U, which isequal to or smaller than a diameter of the lens U. As a result, theultraviolet curing resin is cured as shown in FIG. 7 and FIG. 8.Thereafter, a light diffusion portion 22 is formed by removing a portionthat has not been cured. Subsequently, the light diffusion layer 20C isformed by forming a transparent portion 42 between light diffusionportions 22. In addition, this light diffusion layer 20C may be formedby removing a part of a light diffusion layer 20A according to the firstembodiment using a photolithography or sputtering method. Of course, thepresent invention is not limited by the method for forming the lensarray sheet.

(Example of Advantages of Lens Array Sheet 106)

Hereinbefore, a configuration of the lens array sheet 106 and the likeaccording to the sixth embodiments of the present invention have beendescribed. This lens array sheet 106 can have an advantage that a shapeof an interface between a light diffusion portion 22 and a transparentportion 42 has a shape following a light focusing region G in additionto the advantages achieved by the lens array sheet 103 according to thethird embodiment. Therefore, a part of light diffused by the lightdiffusion portion 22 can be reflected by the difference in therefractive index at the interface and an amount of light directingtoward a corresponding lens U can be increased. In other words, the lensarray sheet 106 according to the sixth embodiment enables in effect thelight to be guided toward the lens U by the interface between the lightdiffusion portion 22 and the transparent portion 42. Consequently, thelens array sheet 106 also enables a light use efficiency to be improved.

Hereinbefore, the embodiments (the first embodiment to the sixthembodiment) classified into one group of the present invention have beendescribed. In the above mentioned first to sixth embodiments, it isshown that light diffusion layers 20A, 20B and 20C, and a lightreflection layer 30 forms individual layers. However, a lens array sheetcan be formed by embedding light reflection portions 31 of the lightreflection layer 30 in the light diffusion layers 20A, 20B and 20C,respectively. In other embodiments (a seventh embodiment to a tenthembodiment) classified into the other group of the present invention, alight reflection portion is embedded in a light diffusion layer. Sincethe light diffusion layer is embedded with the light reflection portionin this manner, the light diffusion layer enables a light use efficiencyto be improved. We will describe hereinafter seventh, eighth, ninth, andtenth embodiments in detail. Referring to FIG. 9, a lens array sheetaccording to the seventh embodiment will now be described.

Lens Array Sheet 201 According to Seventh Embodiment

FIG. 9 is an explanatory diagram for explaining a configuration of alens array sheet according to the seventh embodiment of the presentinvention.

(Configuration of Lens Array Sheet 201)

As shown in FIG. 9, a lens array sheet 201 according to this embodimenthas a light diffusion layer 50A in place of a light diffusion layer 20Aand a light reflection layer 30 included in a lens array sheet 101according to the first embodiment. In addition, the light diffusionlayer 50A has a light diffusion portion 21 and a light reflectionportion 51. On one hand, as shown in FIG. 9, a light diffusion portion21 according to this embodiment has a layered shape that is differentfrom that of a light diffusion portion 21 forming a light diffusionlayer 20A according to the first embodiment, and is denoted by the samereference as that in the first embodiment. On the other, thought thelight reflection portion 51 according to this embodiment is denoted by adifferent reference from that in the first embodiment due to the factthat the light reflection portion 51 is formed by embedding it in thelight diffusion layer 50A, the light reflection portion 51 may be inprinciple formed in the same manner as light reflection portions 31 and32 according to the first to sixth embodiments.

The light diffusion portion 21 is laminated on a flat surface of a lenslayer 10 and formed integrally with the lens layer 10. Then, the lightdiffusion layer 50A diffuses light passing through it.

The light reflection portion 51 is embedded in the light diffusionportion 21 at least within a part of a non-light focusing region N of alens U. In short, the light reflection portion 51 is embedded in a planein parallel with a lens array sheet 201 such that the light reflectionportion 51 covers a light focusing region. In addition, the lightreflection portion 51 reflects light passing through the non-lightfocusing region N and directing toward the lens layer 10.

(Example of Method for Forming Lens Array Sheet 201)

Such light diffusion layer 50A may be formed, for example, as follows.For example, first, a light diffusion portion 21 is formed on a flatsurface of the lens layer 10 as a flat layered structure and a recess isformed on a back side of the light diffusion portion 21 by a lithographymethod or a sputtering method. The light diffusion layer 50A is thenformed by applying a light reflection portion 51 on the recess.Alternatively, the light diffusion layer 50A may be formed, for example,by evenly forming a part of the light diffusion portion 21 on the flatsurface of the lens layer 10, further laminating the light diffusionportion 21 having a recess of a predetermined pattern on the part of thelight diffusion portion 21, and thereafter applying the light reflectionportion 51 on the recess. Of course, the present invention is notlimited by the method for forming the lens array sheet.

(Example of Advantages of Lens Array Sheet 201)

Hereinbefore, a configuration of the lens array sheet 201 and the likeaccording to the seventh embodiment of the present invention have beendescribed. This lens array sheet 201 can have an advantage that itenables a reflectance of the light reflection portion 51 to be improved,and a light use efficiency to be also improved by adjusting a thicknessof the light reflection portion 51 in addition to the advantagesachieved by the lens array sheet 101 according to the first embodiment.The light reflection portion 51 may serve to restrict light, which isincident on the lens layer 10, to light passing through a focal point Fas in the case of the light reflection layer 30 and the like accordingto the first embodiment. However, though a metal material is used, forexample, for the light reflection layer 30, the light reflection layer30 enables absorption or transmission of light to be generated and areflectance is not equal to 100%. When the reflectance is low, lightactually reflected by the lens layer 10 would be reduced due to theabsorption or transmission of the light at the light reflection portion51. To the contrary, the light reflection portion 51 enables thereflectance to be improved by thickening a thickness of the lightreflection portion 51. In this manner, when the thickness of the lightreflection portion 31 in the first embodiment and the like is thickened,a thickness of the lens array sheet 201 by itself would be thickened.However, the thickness of the light reflection portion 51 can be easilythickened without increasing the thickness of the light reflectionportion 51 by itself, when the light reflection portion 51 is embeddedin the light diffusion layer 50A. In addition, it is desirable that adepth by which this light reflection portion 51 is embedded in the lightdiffusion layer 50A, that is to say, the thickness of the lightreflection portion 51 is configured such that reflection efficiencyreaches equal to or more than 70%. Furthermore, it is desirable thatthis thickness is configured such that a reflectance becomes equal to ormore than 80%, more preferably equal to or more than 90%. In addition,it is desirable that this thickness is configured depending on amaterial of the light reflection portion and the like, because thethickness varies depending on its material and the like.

The lens array sheet 106 according to the sixth embodiment enables lightto be guided toward a lens U using an interface between a lightdiffusion portion 22 and a transparent portion 42 by arranging thetransparent portion 42 between light diffusion portions 22. The lensarray sheet 201 according to this embodiment enables light to be guidedtoward a lens U using a light reflection portion 51, which has a higherefficiency than the interface, by embedding the light reflection portion51 in the light diffusion portion 21. Therefore, embodiments will laterbe described that modifies a shape of the light reflection portion 51 inorder to improve such light guidance effect. First, for the purpose ofdescribing such embodiments, eighth and ninth embodiments of the presentinvention will be described with reference to FIGS. 10, 11 and 12.

Lens Array Sheets 202 and 203 According to Eighth and Ninth Embodiments

FIG. 10 is an explanatory diagram for explaining a configuration of alens array sheet according to an eighth embodiment of the presentinvention. FIG. 11 and FIG. 12 illustrate a configuration of a lensarray sheet according to a ninth embodiment of the present invention.

(Configuration of Lens Array Sheets 202 and 203)

As shown in FIGS. 10 and 11, each of lens array sheets 202 and 203 haslight diffusion layers 50B and 50C in place of a light diffusion layer50A included in a lens array sheet 202 according to the seventhembodiment. In addition, these light diffusion layers 50B and 50C havelight reflection portions 52 and 53, respectively, in place of a lightreflection portion 51.

The light reflection portions 52 and 53 are embedded in a lightdiffusion portion 21 at least within a part of a non-light focusingregion N of a lens U as in the case of the light reflection portion 51.In short, the light reflection portions 52 and 53 are also embedded in aplane in parallel with the lens array sheets 202 and 203 such that thelight reflection portions cover a light focusing region. In addition,the light reflection portions 52 and 53 also reflect light passingthrough the non-light focusing region N and directing toward a lenslayer 10.

In addition, each of the light reflection portions 52 and 53 has a shape(a width in a direction of a plane in each of lens array sheets 202 and203) gradually narrowing toward the lens layer 10. In other words, eachof the light reflection portions 52 and 53 has a shape following thenon-light focusing region N of individual lenses U. Furthermore, thelight reflection portions 52 and 53 serve to riot only reflect lightpassing through the non-light focusing region N and directing toward thelens layer 10, but also reflect and return light, which is diffused at alight diffusion portion 21 and departs from a light focusing region G,to the light focusing region G.

(Example of Dimensions of Lens Array Sheet 203)

Hereinbefore, a configuration of the lens array sheets 202 and 203 havebeen described.

Referring to FIG. 12, an example of dimensions of individualconfigurations in the lens array sheet 203 and the like will now bedescribed as an example of a lens array sheet in which graduallynarrowing light reflection portions 52 and 53 are embedded.

FIG. 12 illustrates a lens layer 10 and a light diffusion layer 50Ccorresponding to a single lens U. A width of a single lens is denoted byL and a distance from a flat surface of the lens layer 10 to a focalpoint F is denoted by S. In addition, a depth from the lens layer 10 inthe light diffusion layer 50C is denoted di, a width of the lightdiffusion layer 50C at the depth di is denoted by Wj, and a depth atwhich a light reflection portion 53 is embedded in the light diffusionlayer 50C is denoted by f. Then, the width Wj of the light reflectionportion 53 can be set to satisfy the following condition (Formula 3).

$\begin{matrix}{{Wj} \leq \left\{ \begin{matrix}\frac{L \times {dj}}{2 \times S} & {{{or}\mspace{14mu} {Wj}} = 0} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \geq {di}} \\{L\left( {- \frac{dj}{2S}} \right)} & {{{or}\mspace{14mu} {Wj}} = 0} & \ldots & {{{in}\mspace{14mu} {case}\mspace{14mu} S} \leq {di}}\end{matrix} \right.} & \left( {{Formula}\mspace{14mu} 3} \right)\end{matrix}$

As described above, a reflectance of the light reflection portion 53depends on the depth f at which the light reflection portion 53 isembedded in the light diffusion layer 50C. Therefore, it is desirablethat this depth f is configured such that the reflectance in the lightreflection portion 53 becomes equal to or more than 70%. Furthermore, itis desirable that the depth f is configured such that the reflectancereaches equal to or more than 80%, more preferably, 90%.

(Example of Method for Forming Lens Array Sheets 202 and 203)

Such light diffusion layers 50B and 50C may be formed, for example, asin the case of a light diffusion layer 50A as follows. In short, forexample, a light diffusion portion 21 is initially formed in a flatlayered shape on a flat surface of a lens layer 10 and a recess is thenformed on a back side of the light diffusion portion 21 using aphotolithography method or a sputtering method. In addition, the lightdiffusion layers 50B and 50C are formed by applying a light reflectionportion 52 or 53 on the recess. Alternatively, the light diffusionlayers 50B and 50C may be formed by forming a part of the lightdiffusion layer 21 on the flat surface of the lens layer 10, furtherlaminating the light diffusion layer 21 having a recess of apredetermined pattern on the part of the light diffusion portion 21, andthereafter applying the light reflection portion 52 or 53 on the recess.

Furthermore, the light diffusion layer 50C may be formed, for example,using an ultraviolet curing resin. In this case, for example, a layeredlight diffusion portion 21 is initially formed, and a material that canbe cured by heat and ultraviolet light is applied across the lightdiffusion portion 21. A lens array sheet is then arranged on the otherside of the light diffusion portion 21 with a pitch similar to that ofthe lens layer 10, where a lens having a shorter focal distance thanthat of a lens U is arranged on the lens array sheet. This lens arraysheet is then irradiated by light so as to be cured. Thereafter, thelens array sheet is removed, the lens layer 10 is bonded, and uncuredultraviolet curing resin is removed, so that a light reflection portion53 is applied on a portion from which the lens array sheet has beenremoved. As a result, it is possible to form the light diffusion layer50C. Of course, the present invention is not limited by the method forforming the lens array sheet.

(Example of Advantages of Lens Array Sheets 202 and 203)

Hereinbefore, a configuration of the lens array sheets 202 and 203 andthe like according to the eighth and ninth embodiments of the presentinvention have been described. These lens array sheets 202 and 203 canhave an advantage that a shape of each of the light reflection portions52 and 53 has a shape following a non-light focusing region N inaddition to the advantages achieved by the lens array sheet 103according to the seventh embodiment. Therefore, a part of light diffusedby the light diffusion portion 21 can be reflected by the lightreflection portions 52 and 53, and an amount of light directing toward acorresponding lens U can be increased. In other words, the lens arraysheets 202 and 203 according to the eighth and ninth embodiments,respectively, enable in effect the light to be guided toward the lens Uby the light reflection portions 52 and 53. Consequently, the lens arraysheets 202 and 203 also enable a light use efficiency to be improved.

The lens array sheets 202 and 203 according to the eighth and ninthembodiments, respectively, are shown such that each of the lightreflection portions 52 and 53 has a width gradually narrowing toward thelens layer 10. In other words, it is shown that each of the lightreflection portions 52 and 53 has a shape following the non-lightfocusing region N, and the light diffusion portion 21 has a shapefollowing a light focusing region G. However, the shape of each of thelight reflection portions 52 and 53 is not limited to this example, butmay be further modified. Therefore, referring to FIG. 13, a tenthembodiment of the present invention will now be described in that alight reflection portion has a different shape.

Lens Array Sheet 204 According to Tenth Embodiment

FIG. 13 is an explanatory diagram for explaining a configuration of alens array sheet according to a tenth embodiment of the presentinvention.

(Configuration of Lens Array Sheet 204)

As shown in FIG. 13, a lens array sheet 204 has light diffusion layers50D in place of a light diffusion layer 50A included in a lens arraysheet 201 according to the seventh embodiment. In addition, this lightdiffusion layer 50D has a light reflection portion 54 in place of alight reflection portion 51.

The light reflection portion 54 is embedded in a light diffusion portion21 at least within a part of a non-light focusing region N of a lens Uas is the case of the light reflection portion 51. In short, the lightreflection portion 54 is also embedded in a plane in parallel with thelens array sheet 204 such that the light reflection portion covers alight focusing region. In addition, the light reflection portion 54 alsoreflects light passing through the non-light focusing region N anddirecting toward a lens layer 10.

In addition, the light reflection portion 54 has a shape (a width in adirection of a plane in the lens array sheet 204) gradually wideningtoward the lens layer 10. Furthermore, the light reflection portion 54serves to not only reflect light passing through the non-light focusingregion N and directing toward the lens layer 10, but also reflect andreturn light, which is diffused at a light diffusion portion 21 anddeparts from a light focusing region G, to the light focusing region G.

(Example of Method for Forming Lens Array Sheet 204)

Such light diffusion layer 50D may be formed, for example, using aphotolithography method or a sputtering method. In this case, forexample, a portion in which a light reflection portion 54 is to beembedded is previously formed. In short, a layered light diffusionportion 21 is provided and a recess is formed from a direction, in whicha lens layer 10 is arranged, by the photolithography method or thesputtering method. The light reflection portion 54 is then formed in therecess, and subsequently the layered diffusion portion 21 is furtherlaminated on the reflection portion. In addition, the lens layer 10 isbonded to the laminated layered light diffusion portion 21 to completethe lens array sheet 204.

Furthermore, the light diffusion layer 50D may be formed using anultraviolet curing resin as in the case of the eighth and ninthembodiments. In this case, a lens layer 10 is initially formed and alayered light diffusion portion 21 is formed on a flat surface of thelens layer 10. An ultraviolet curing resin is then applied on thelayered light diffusion portion 21 and subsequently a lens layer similarto the lens layer 10 is arranged at an opposite side to the lens layer10. In addition, a part of the ultraviolet curing resin is irradiatedand cured with ultraviolet light from a side of this newly arranged lenslayer. Thereafter, the lens layer and the remaining uncured ultravioletcuring resin are removed. Since a recess is formed at a position fromwhich the ultraviolet curing resin has been removed, a light reflectionportion 53 is then applied on the recess. As a result, the lens arraysheet is completed. Of course, the present invention is not limited bythe method for forming the lens array sheet.

(Example of Advantages of Lens Array Sheet 204)

Hereinbefore, a configuration of the lens array sheet 204 and the likeaccording to the tenth embodiment of the present invention have beendescribed. The lens array sheets 204 can have an advantage that a widthof the light reflection portion 54 is gradually widened toward the lenslayer 10 in addition to the advantages achieved by the lens array sheet103 according to the seventh embodiment. For example, a part of lightpassing between one light reflection portion 54 and a neighbor lightreflection portion 54 (i.e., a part of light passing through “anopening”) is diffused by the light reflection portion 54 and directstoward a lens U different from a lens U corresponding to the opening. Inthis case, the light reflection portion 54 has a shape such that anincident angle of light directing toward a direction of other lensesincreases. Therefore, it is possible to reflect the light directingtoward the direction of the other lenses to a light focusing region G ofthe primarily corresponding lens U and efficiently suppress crosstalkthat is incident on the other lenses. Consequently, the lens array sheetenables a light use efficiency and conversion efficiency to generallyparallel light by the lens layer 10 to be improved.

Hereinbefore, the lens array sheets according to various embodiments ofthe present invention have been described.

A lens array sheet incorporated a liquid display device and the likewill now be described. For this purpose, lens array sheets according tothe first to tenth embodiments are generally referred to as a “lensarray sheet 300”. Any of the lens array sheets according to the first totenth embodiments is operable to reduce moire fringes while maintainingthe image quality, as described above.

Liquid Crystal Display Device 400 According To Eleventh Embodiment

FIG. 14 is an explanatory diagram for explaining a configuration of aliquid crystal display device according to an eleventh embodiment of thepresent invention.

A liquid crystal display device 400 according to this embodiment has aliquid crystal panel 403 and a light source 401.

The liquid crystal panel 403 has a plurality of pixels, which areregularly arranged, and enables a predetermined image or video to bedisplayed by controlling transmission and blocking of light emitted fromthe light source 401 for each of the pixels. To this end, liquid crystalmolecules are arranged in each of the pixels in the liquid crystal panel403. In addition, a particular polarizing filter is arranged in frontand in the rear of the liquid crystal molecules. Orientation of theliquid crystal molecules is changed by controlling a voltage applied tothe liquid crystal molecules. As a result, transmission and blocking ofthe light is controlled by the polarizing filter and the orientation ofthe liquid crystal molecules.

The light source 401 is arranged at a back side of the liquid crystalpanel and emits light to the liquid crystal panel 403. To this end, thelight source 401 has a backlight 405 and an optical sheet 402.

The backlight 405 emits light (e.g., white light) to the optical sheet.The back light 405 includes, for example, but not limiting to, adischarge lamp such as a cold cathode fluorescent lamp (CCFL), anelectroluminescence (EL) lamp such as a light emitting diode (LED) andthe like.

The optical sheet 402 has a lens array sheet 300 and a light diffusionplate 404.

The light diffusion plate 404 is arranged in front of the backlight 405and reduces unevenness in light intensity by diffusing light emittedfrom the backlight 405. In short, the light diffusion plate 404 cancelsan image of a lamp and the like constituting the backlight 405, andequalizes light intensity. This diffusion plate 404 may be, for example,formed of a material similar to that of light diffusion portions 21 and22 in the first to tenth embodiments as described above.

The lens array sheet 300 is arranged in front of the light diffusionplate 404 and just the same as the lens array sheet according to any ofthe first to tenth embodiments in that the lens array sheet 300increases a component of generally parallel light in the light radiatedfrom the light diffusion plate 404. Therefore, the lens array sheet 300initially restricts the diffused light, which is incident from the lightdiffusion plate 404, to a focal point of a lens by means of a lightreflection portion and the like, and increases the component of theparallel light by means of a lens layer. In short, the lens array sheet300 increases the component of the light directing toward a frontdirection (normal direction) of the liquid crystal display device 400.In addition, the lens array sheet 300 supplies light to the liquidcrystal panel 403. Therefore, the lens array sheet 300 enablesbrightness, an optical viewing angle, contrast ratio of the liquidcrystal display device 400, and the like to be improved and therebyimproving the image quality.

In this case, the lens array sheet 300 diffuses the light restricted bythe light diffusion portion and the like and directing toward the lenslayer. Therefore, the light emitted from the lens array sheet 300 issuch that the component of the generally parallel light has beenincreased, the light has been adequately diffused, and a light and darkpattern as well as a directional pattern due to a lens pitch of the lenslayer and a structured pattern of the light reflection portion and thelike are reduced. As a result, a light pattern that interferes with thestructured pattern of the pixels in the liquid crystal panel 403 andproduce moire fringes is reduced by the lens array sheet 300.Consequently, the lens array sheet 300 is operable to improve the imagequality, as described above, and suppress the moire fringes from beingproduced.

Hereinbefore, the liquid crystal display device 400 according to theeleventh embodiment of the present invention has been described.

Referring to FIG. 15, a liquid crystal display device according to atwelfth embodiment of the present invention will now be described.

Liquid Crystal Display Device 400 According To Twelfth Embodiment

FIG. 15 is an explanatory diagram for explaining a configuration of theliquid crystal display device according to the twelfth embodiment of thepresent invention.

As shown in FIG. 15, the liquid crystal display device 500 according tothe twelfth embodiment has a polarization splitting film 503 and a lightdiffusion film 504 in addition to the configurations incorporated in theliquid crystal display device 400 according to the eleventh embodiment.In FIG. 15, since a light source 501 and an optical sheet 502 have thepolarization splitting film 503 and the light diffusion film 504, thelight source 501 and the optical sheet 502 are designated by differentreferences from those of the light source 401 and the optical sheet 402in the liquid crystal display device 400 according to the eleventhembodiment.

The polarization splitting film 503 is arranged at a back side of aliquid crystal panel 403 and is a brightness improving film thatimproves brightness of the liquid crystal display device 500. Forexample, a film having a reflected polarization may be used for thepolarization splitting film 503. A reflected polarization film transmitsonly light having a vibration direction in parallel with one axis in aplane, and reflects other light. Such reflected polarization film mayinclude, for example, a brightness enhancement film such as DBEF (tradename) series and DRPF-H (trade name) series manufactured by 3M, Inc.Alternatively, a circular polarized light film may be used in place ofsuch linear polarized light film. The circular polarized light film mayinclude, for example, a film having a cholesteric circular polarizersuch as Nipocs (trade name) manufactured by Nitto Denko Corporation.

The light diffusion film 504 is arranged between the polarizationsplitting film 503 and the lens array sheet 300, and diffuses lightemitted from the lens array sheet 300. In addition, the light diffusionfilm 504 also diffuses light reflected from the polarization splittingfilm 503. Such light diffusion film 504 may be, for example, formed of amaterial similar to that of the light diffusion portions 21 and 22 inthe first to tenth embodiments.

As the liquid crystal display device 500 is provided with thesepolarization splitting film 503 and light diffusion film 504, the liquidcrystal display device 500 is also operable to improve its brightness.This brightness improving mechanism will be now described as follows. Atfirst, light having its parallel light component, which is increased bythe lens array sheet 300, is diffused by the light diffusion film 504and is incident on the polarization splitting film 503. The polarizationsplitting film 503 then transmits light in a vibration direction inparallel with one axis and reflects other light. The light reflected bythe polarization splitting film 503 is again incident on the lightdiffusion film 504. The light, which is again incident on the lightdiffusion film 504, is again diffused and a part of the diffused lightis again incident on the polarization splitting film 503. Thepolarization splitting film 503 transmits once again a light in thevibration direction in parallel with the one axis and reflects the otherlight. In a usual liquid crystal display device, a use efficiency offront face brightness to light irradiated by a backlight reaches about40%. However, by repeatedly transmitting and reflecting the light by thepolarization splitting film 503, polarized light can be irradiated tothe liquid crystal panel 403. As a result, the liquid crystal displaydevice 500 according to this embodiment enables a light use efficiencyto be improved, for example, to an extent equal to or more than 50%.

Of course, an arrangement position of the light diffusion film 504 isnot limited to a position between the polarization splitting film 503and the lens array sheet 300, but may be a position between the lensarray sheet 300 and the light diffusion plate 404. In addition, sincethe lens array sheet 300 according to each of the various embodiments ofthe present invention has the light diffusion portion 21 and 22 and thelike, the lens array sheet 300 is operable to serve as the lightdiffusion film 504. In this case, the light diffusion film 504 may bedispensed with.

Hereinbefore, the lens array sheet and the liquid crystal display deviceaccording to each of the embodiments of the present invention have beendescribed. Examples of the lens array sheet and the liquid crystaldisplay device will now be described.

EXAMPLE

First, lens array sheets 101 to 105 according to the first to fifthembodiments, respectively, and lens array sheets 201 to 204 according tothe seventh to tenth embodiments, respectively, were created. In thiscase, a lens layer and a transparent portion contained in each of thelens array sheets were formed of an acrylic resin and a light diffusionportion is formed of an acrylic resin having silica dispersed therein.In addition, a light reflection layer was formed of a urethane resinmixed with a white pigment. A shape of each of configurations wasconfigured such that a haze value of each of light diffusion layers wasequal to 20%.

A liquid crystal display device 400 according to the eleventhembodiment, as shown in FIG. 14, was then created for each of the lensarray sheets. In this case, a backlight 405 and a light diffusion plate404 were implemented by a backlight and a light diffusion plate ofKDL-40X5000 (trade name) contained in a liquid crystal televisionmanufactured by Sony Corporation and available in the market.

Thus, formed liquid crystal display device was subject to visualobservation in order to detect whether there were any moire fringes, andfront face brightness of each of the liquid crystal display devices wasalso measured by “CS-1000 (trade name)” manufactured by Konica MinoltaSensing, Inc.

Furthermore, liquid crystal display devices similar to theabove-mentioned one, except for a lens array sheet, were provided ascomparative examples. As Comparative Example 1, a liquid crystal displaydevice having no lens array sheets was provided. As Comparative Example2, a liquid crystal display device was provided that had a lens arraysheet including a transparent layer in place of a light diffusion layer20A in a lens array sheet 101 according to the first embodiment as shownin FIG. 1. As Comparative Example 3, a liquid crystal display device wasprovided that had a lens array sheet including a transparent portion inplace of a light diffusion portion 21 in a lens array sheet 201according to the seventh embodiment as shown in FIG. 9. Thesecomparative examples were also subject to the same visual observationand measurement as those of the examples.

Table 1 shows results of the observation and the measurement.

As can be seen in Table 1, moire fringes were produced in ComparativeExamples 2 and 3 where the liquid crystal display devices had no lightdiffusion portions 21 and the like, whereas moire fringes weresuppressed from being produced in the liquid crystal display device ineach of the embodiments of the present invention. It is supposed that nomoire fringes were produced in the liquid crystal display device inComparative Example 1, because no light and dark patterns interferingwith a structured pattern of a liquid crystal panel were generated dueto the fact that the liquid crystal display device had no lens arraysheets. However, in the liquid crystal display device in ComparativeExample 1, since it had no lens array sheets, the front face brightnesswas decreased.

In addition, it can be seen that the front face brightness in the liquidcrystal display device of each of the embodiments was much improved thanthat of Comparative Example 1 where the liquid crystal display devicehad no lens array sheets. In particular, in the second to fifthembodiments, the front face brightness was further improved due totransparency achieved by transparent portions 41 and 42 and the like,and an effect of guiding light toward a lens U by an interface of eachof the transparent portions. Furthermore, in the seventh to tenthembodiments, the front face brightness was further improved, becauselight reflection portions 51 to 54 were embedded in light diffusionlayers 50A to 50B and light was further effectively guided to the lens Uby means of the light reflection portion 51.

TABLE 1 FRONT FACE LENS SHEET PRODUCTION BRIGHTNESS EMBODIMENTS OF MOIRE(cd/m²) FIRST EMBODIMENT NO 518 SECOND EMBODIMENT NO 527 THIRDEMBODIMENT NO 520 FORTH EMBODIMENT NO 529 FIFTH EMBODIMENT NO 531SEVENTH EMBODIMENT NO 533 EIGHTH EMBODIMENT NO 551 NINTH EMBODIMENT NO541 TENTH EMBODIMENT NO 536 COMPARATIVE EXAMPLE 1 NO 505 COMPARATIVEEXAMPLE 2 YES 535 COMPARATIVE EXAMPLE 3 YES 571

Subsequently, a haze value of a light diffusion layer included in thelens array sheet according to each of the embodiments was measured. Inshort, five different lens array sheets were created that had the samestructure as that of the lens array sheet 101 according to the firstembodiment, but had light diffusion layer 20A of different haze values,respectively. Liquid crystal display devices were then formed in similarmanner as described above using individual lens array sheets. Inaddition, the haze value of each of the lens array sheet was measuredusing a haze meter HR-100 (trade name) manufactured by MURAKAMI COLORRESEARCH LABORATORY. The liquid crystal display devices includingrespective lens array sheets having the different haze values were alsosubject to the visual observation in order to detect whether there wereany moire fringes and front face brightness of each of the liquidcrystal display devices was also measured.

Table 2 shows results of the observation and the measurement.

As can be seen in Table 2, no moire fringes were produced, but the frontface brightness was reduced in the liquid crystal display devices havingthe haze value more than 20%. Therefore, the light diffusion layerincluded in the lens array sheet according to each of the embodiments ispreferably formed such that the haze value is decreased equal to or lessthan 20% because decrease of the front face brightness is maintainedcomparatively low at that haze value.

TABLE 2 FRONT FACE HAZE VALUE OF LIGHT PRODUCTION BRIGHTNESS DIFFUSIONLAYER OF MOIRE (cd/m²)  9% NO 527 20% NO 518 31% NO 470 42% NO 450 49%NO 421 COMPARATIVE EXAMPLE 2 YES 535

Furthermore, a liquid crystal display device 500 according to thetwelfth embodiment, as shown in FIG. 15, was formed and the liquidcrystal display device was also subject to the observation in order todetect whether there were any the moire fringes. In this case, abrightness improving film, DBEF (trade name) series manufactured by 3M,Inc. was used as a polarization splitting film 503. As a result,production of the moire fringes was not observed in the liquid crystaldisplay device 500. Therefore, the liquid crystal display device 500also enables the moire fringes to be suppressed from being produced withor without the polarization splitting film 503.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2008-105980 filedin the Japan Patent Office on Apr. 15, 2008, the entire content of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A lens array sheet comprising: a lens layer having a lens surface onwhich a plurality of lenses are formed in an array; a light reflectionlayer arranged at an opposite side to the lens surface of the lens layerand having an opening within a light focusing region in the lenses totransmit light, for reflecting light at a site other than the opening;and a light diffusion layer arranged between the lens layer and thelight reflection layer, for diffusing light, which passes through theopening and is directed toward the lens layer.
 2. The lens array sheetaccording to claim 1, wherein the light diffusion layer includes aplurality of light diffusion portions arranged within the light focusingregion in the lenses, for diffusing the light passing through theopening and directing toward the lens layer; and transparent portionsarranged between the plurality of light diffusion portions, fortransmitting the light.
 3. The lens array sheet according to claim 2,wherein each of the light diffusion portions has a shape such that awidth of the shape gradually widens toward the lens layer.
 4. The lensarray sheet according to claim 1, wherein the lens array sheet furthercomprises a transparent layer arranged between the light diffusion layerand the light reflection layer, for transmitting the light.
 5. The lensarray sheet according to claim 1, wherein the lens array sheet furthercomprises a transparent layer arranged between the lens layer and thelight diffusion layer, for transmitting the light.
 6. The lens arraysheet according to claim 1, wherein a haze of the light diffusion layeris equal to or less than 20%.
 7. The lens array sheet according to claim1, wherein the light reflection layer is a scatter and reflection layerfor scattering light in order to reflect the light.
 8. The lens arraysheet according to claim 1, wherein the light reflection layer is notformed at least around the lens array sheet.
 9. The lens array sheetaccording to claim 1, wherein a lenticular lens is formed on the lenssurface of the lens layer and the lenticular lens includes a pluralityof convex shapes arranged in parallel to each other and at apredetermined distance.
 10. A light source comprising: a lens arraysheet having a lens surface on which a plurality of lenses are formed inan array; and a backlight arranged at an opposite side to the lenssurface of the lens array sheet, for emitting light on the lens arraysheet, wherein the lens array sheet includes: a lens layer having thelens surface; a light reflection layer arranged at an opposite side tothe lens surface of the lens layer and having an opening within a lightfocusing region in the lenses to transmit the light emitted from thebacklight, for reflecting light at a site other than the opening; and alight diffusion layer arranged between the lens layer and the lightreflection layer, for diffusing the light passing through the openingand directing toward the lens layer.
 11. A liquid crystal display devicecomprising: a lens array sheet arranged between a liquid crystal paneland a backlight emitting light on the liquid crystal panel and having,at a side of the liquid crystal panel, a lens surface on which aplurality of lenses are formed in an array, wherein the lens array sheetincludes: a lens layer having the lens surface; a light reflection layerarranged at an opposite side to the lens surface of the lens layer andhaving an opening within a light focusing region in the lenses totransmit the light emitted from the backlight, for reflecting light at asite other than the opening; and a light diffusion layer arrangedbetween the lens layer and the light reflection layer, for diffusing thelight passing through the opening and directing toward the lens layer.